1. Field of the Invention
This invention relates to the treatment of living tissues and/or cells by altering their interaction with charged species in their environment. More particularly, the invention relates to an electromagnetic body treatment device and method for surgically non-invasive modification of the growth, repair and maintenance behavior of living tissues and cells by a specific and selective change in their electrical environment. Still more particularly, this invention provides for the application by a surgically non-invasive direct inductive coupling of an electrical voltage and current signal of a highly specific frequency and power, for the prevention of osteoporosis or the enhancement of new bone tissue formation.
2. Description of the Prior Art
Ryaby, et al. U.S. Pat. Nos. 4,105,017, 4,266,532, 4,266,533 and 4,315,503 collectively describe means and methods for effecting surgically non-invasive direct inductive coupling to an afflicted body region, whereby one or more electric voltage and concomitant current signals conform to a highly specific pattern and are said to have been found to develop therapeutically beneficial treatment of the afflicted region, as for example in the enhancement of repair of bone fractures, non-unions, and the like.
The methods described in one or more of the above mentioned Ryaby, et al. patents employ an asymmetrical waveform which is induced in the tissue or cells by the alternate energization and de-energization of an electromagnetic coil. FIGS. 5a and 5b of the drawings of each of the above Ryaby, et al. patents illustrate such typical asymmetrical waveforms which are induced in the tissue or cells.
For example, in what Ryaby, et al. describe in U.S. Pat. No. 4,315,503 as a Mode 1 signal (illustrated by FIG. 5a of the '503 patent), the asymmetrical waveform includes positive pulse portions P1 comprising three segments 39, 40 and 41, and a negative pulse portions P2. The frequency of the Mode 1 signal is described as being about 10 to 100 Hertz with a duty cycle of 20 to 30 percent. The average amplitude of the negative portion of the waveform is described as being no greater than about 1/6 the average amplitude of the positive pulse portion. The average amplitude of the positive pulse portion is described as being within the range of about 0.0001 to 0.01 volts per centimeter of tissue or cells, which corresponds to between about 0.1 and 10 microamperes per square centimeter of treated tissue and/or cells. An induced waveform having a positive pulse portion with a peak amplitude of between about 1 and 3 millivolts per centimeter of treated tissue, corresponding to 1 to 3 microamperes per square centimeter of treated tissue and/or cells, with the duration of each positive pulse portion being about 300 microseconds and the duration of each negative pulse portion of about 3300 microseconds, and a pulse repetition rate of about 72 Hertz, is stated to represent a preferred and optimum induced pulse signal for the treatment of bone disorders. A preferred treatment regime using Mode 1 type signals is described as having been found to be a minimum of 8 hours per day for a period of four months in difficult cases, and two weeks in less difficult cases.
The Ryaby, et al. patents, such as U.S. Pat. No. 4,315,503, also describe a Mode 2 type asymmetrical waveform, illustrated by FIG. 5b of the '503 patent, which waveform is induced in the tissue or cells. The Mode 2 type signal is applied in a pulse-train modality, which contains bursts (pulse groups) of asymmetrical waveforms. Each burst portion of the signal contains a series of pulses having positive and negative portions. Each positive pulse portion is described as including three segments 39', 40' and 41'. The peak negative amplitude of the negative pulse portion is stated as preferably not being more than about 40 times the peak amplitude of the positive pulse portion. The duration of each positive pulse portion is described as being at least about four times the duration of the following negative pulse portion. The pulse repetition rate of the pulses within the burst segment of the Mode 2 pulse train is described as possibly being between about 2,000 Hertz and 10,000 Hertz.
It is stated in the Ryaby, et al. patents, such as the '503 patent, that the average magnitude of the positive peak potential of the Mode 2 type signal should be within the range of about 0.00001 to 0.01 volts per centimeter of tissue and/or cells, which corresponds to about 0.01 to 10 microamperes per square centimeter of treated tissue and/or cells. It is further stated that the repetition rate of the burst segment should be within the range of about 5 to 15 Hertz for bone and other hard tissues. It is further described that each negative pulse portion within the burst segment of the pulse train should be of a duration no greater than about 50 microseconds and of an average amplitude no greater than 50 millivolts per centimeter of treated tissue and/or cells, corresponding to about 50 microamperes per square centimeter of treated tissue and/or cells.
The Ryaby, et al. patents further state that for the treatment of bone disorders using a Mode 2 type signal, an optimum induced positive pulse signal portion has a peak amplitude of between about 1 and 3 millivolts per centimeter of treated tissue, which corresponds to 1 to 3 microamperes per square centimeter of treated tissue and/or cells, with a duration of each positive pulse portion being about 200 microseconds and the duration of each of the negative pulse portions being about 30 microseconds, a pulse repetition rate of about 4,000 Hertz, a burst segment width of about 5 milliseconds, and a burst repetition rate of about 10 Hertz. The Ryaby et al. patents describe a test-coil procedure to obtain the magnitude of the signal applied, from which the scale of field strength, as used in the patents, corresponds to 65 Tesla per second for each millivolt per centimeter in the tissue.
Although the asymmetrical waveforms described in the Ryaby, et al. patents, and more specifically shown in FIGS. 5a and 5b of those patents, may be suitable to bring about the desired growth or repair of the tissues under treatment, such signals are difficult to reproduce accurately. Expensive equipment and complex circuitry are necessary in order to produce such signals. Such circuitry is shown in FIGS. 7 through 11 of Ryaby, et al. U.S. Pat. No. 4,315,503.
In addition, such equipment does not appear to be portable for certain uses of preferred signals, which limits the ability to apply the recommended signals to only those times spent in the hospital or confined at home. In the extreme case, if such signals are recommended to be applied for eight hours a day during a four month period, one can see how a patient is, for all practicality, confined to the place of treatment.